Vent plug and liquid level indicator for batteries



y 1951 F. M. BROWN EIAL 2,554,557

VENT PLUG AND LIQUID LEVEL INDICATOR FOR BATTERIES Filed Jan. 10, 1948 415 g4 v /f 11 7 l INVENTORY ATTOK/Vly Patented May 29, 1951 UNITED STAT.

"S PATENT QFFICE VENT PLUGAND'LIQUID LEVEL INDICATOR FOR BATTERIES .tionof Delaware Application January 10, 1948,".Serial No. 1,584

SOJai-ms. .1

This invention relates to improved filling and vent plugs for storagebatteries and particularly to a device of this class having an improvedliquid level indicator which facilitates determinations of whether thebattery contains the proper amounts of electrolyte and whenliquid shouldbe added.

,It ,is an object of our invention to provide an unusually inexpensiveand reliable vent plug and liquid level gindicatcr of the class.described.

Another object is to provide a vent plug "with a hollow, translucentliquid level indicator having a lower end adapted to be immersed in theelectrolyte and :so shaped as to reflect upwardly light passing downthrough the open central chamber whereby maximum illumination andunusually clear indications of the liquid level are shown when the plugis viewed from above.

A :further and particular object is to construct a vent plug andintegral level indicator entirely from translucent material wherein alarge central chamber is provided for the passage of light, and thechamber is sealed off from the vent passages and protected from depositsof foreign matter to insure eflicient transmission of light to and froma reflecting surface or surfaces at the lower end of the indicator.

.A further object is to provide a device of the class described with alegend disposed in novel relation to the light reflecting surfaceswhereby the nee-d for additional liquid is clearly indicated when thesurface of the liquid is reduced to a predetermined elevation and thelegend is protected from obscuring deposits of foreign material andagainst exposure .to the electrolyte.

Our invention also includes certain other novel features of constructionwhich will be more fully pointed out in the following specification andclaims.

Referring to the accompanying drawing, which illustrates by way ofexample and not for the purpose of limitation, a preferred form of ourinvention:

Figure 1 is a central vertical section through one of our improved ventplugs in place in "the cover opening of a storage battery cell of common type;

Fig. 2 is a top plan View of one of our improved plugs, showing the darkcentral area which appears when the lower end surfaces are submerged inthe battery electrolyte;

Fig. 3 is a side elevational view of the plug and indicator;

Fig. 4 is a lower end view of the same;

Fig. 5 is a -top plan View showing :the body of the plug with the topclosure member removed;

Fig. 6 is a central vertical section through the separate top closuremember, and

Fig. '7 is a side elevational view of :the lower end portion of analternate form :of liquid level indicator.

In the drawing, the numeral '5! indicates a hollow body member of tourimproved plug which is formed with .a threaded portion 58 adapted to litin the filling opening of a .battery cover =9. Extending downward fromthe body 7 :and integral therewith is :a liquid level indicator Illhaving thin walls defining a large central chamber ii for 'the passageof light to and from a lower end portion :2 of the .indicator. As shownin Figs. 1, 3 and .4, 'thei'lower end portion I2 is of pyramid shape andhas a plurality of reflecting surfaces i3 formed thereon to reflectupwardly light passing down through the central chamber i!. Any numberof suitable reflecting surfaces may be formed on the end portion 12 or,as shown in Fig. 27., a reflecting surface in the shape of a right anglecone lfia may be provided to reflect light up a central chamber Na in alevel indicator illa which is similar to the indicator I'll except inthe matter of the shape of the reflecting surfaces.

Our improved vent :plug and liquid level indicator is preferablyconstructed from a clear plastic such as polystyrene or methylmethacrylate. Such plastics have desirable molding characteristics as'well as suliicient strength durability to make it feasible to constructthe plug with thin, translucent walls, thereby minimiz'ing the cost ofmaterial required for construction of theplug and indicator .andimproving the visibility of the level indications. Other suitabletranslucent materials which are not subject .to attack .by the acid orother electrolyte contained in the battery, e. glass, quartz or suitableplastics not hereinbefore named may be employed in the construction ofour device.

A closure member M for the top of the plug is also constructed from atransparent or transluoent material of the character described. Theperiphery of the member it rests onan-annular shoulder l5 formed in thebody 7. Proiiecting downward, concentric with the periphcry of themember l4 and integral therewith, is an annular flange l ii which isfastened in sealing relation to and in continuation of the walls of theindicator H], along atop surface I! of the walls. The lower end portionof the flange [6 may be fastened and sealed in engagement with thesurface if by the use of suitable cement or solvent whereby the chamberII and the extension thereof defined by the flange I6 and member it areeffectively sealed against'the entry of electrolyte or foreign matter ofany kind, or the flange 16 may be sealed and fastened to the surface llmerely by heat fusion, as by holding the heat softened members togetherunder compression until they fuse and harden in united relation.

An annular chamber i8 is formed in the body I at the outer periphery ofthe flange I6 and communicating with the bottom of this chamber is aplurality of vent passages I9. Other vent passages 24 are formed in thetop closure member I4 through which gases may escape from the batteryand air may enter. In order to afford a clear view into the chamber Hand thence to the reflecting surfaces l3, the-inner and outer surfacesof the member l4 above the chamber I l are polished as are the topsurface 28 and sur faces l3 of the end portion [2. Thecone surface l3aand horizontal surface a of the indicator shown in Fig. 7 are alsopolished.

A suitable legend 21, e. g., Ad Water, is displayed on the surface 20and a similar legend may be displayed on the surface 20a (Fig. 7). Thelegend is preferably embossed on or impressed into the surface which isilluminated only when the level of electrolyte is below the surfaces l3(or [3a, Fig. '7). We prefer to form the legend directly in thetransparent plastic material, without added color to define thecharacters. By so forming the legend we cause it to be obscured orblacked out when thesurfaces E3 or i3a are The reflecting sursubmergedin the electrolyte. faces I3 and l3a are disposed to be immersed in thebattery electrolyte when the latter is approximately at its maximumelevation indicated by the numeral 22 in Fig. 1. As the electrolyteevaporates, its surface elevation is reduced until it is below the lowerextremity of the surfaces l3 or I3a thereby causing the legend 2! toappear clearly when viewed through the transparent closure member [4.When the legend 2| is clearly readable, or when the dark area 23disappears, water or electrolyte should be added. To add liquid, theplug is removed from the filling opening. At all higher levels, thepresence of liquid in contact with the reflecting surfaces l3 or 13a isindicated by the appearance of the dark area at the center of the plugas viewed from above and without removing the plug from the battery. Forexample, the presence of an adequate supply of electrolyte is indicatedby the appearance of a dark area 23 (Fig. 2) which is defined by theintersection of the liquid surface with the reflecting surfaces l3 asreflected to the top of the closure member l4. Such dark areasubstantially completely obscures the legend 2! until furtherevaporation reduces the liquid level and causes the surfaces l3 orsurface l3a to be uncovered. When the surfaces 13 are above the level ofthe liquid, light passing down the indicator is reflected from one ofthe surfaces 13 to the opposite one and then up to the eye of theobserver above the plug thereby giving a bright appearance over theentire indicator surface 20. The dark area indicating the immersion,either in whole or in part, of the surfaces I3 is due to the refractionof the light rays downward into the liquid from the submerged portionsof the surfaces l3. The conical reflecting surface Ba shown in Fig. '7operates in a similar manner to indicate the elevation of the iiquidsurface in the battery cell.

An observer having knowledge that the appearance of a dark areaindicates the presence of liquid at substantially normal elevation doesnot require the further indication of the legend. Accordingly, thelegend is not essential to the operation of our indicator, butconstitutes an advantageous feature which makes the device clearlyunderstandable by observers having no knowledge of or instruction in theoperation of our device.

It will be evident that it is unnecessary to remove the plug todetermine whether liquid should be added to the battery electrolyte.Much time is thereby saved, particularly where a large number of cellsmust be inspected. An unusually clear indication of the level isobtained by reason of the fact that there is a minimum obstruction tothe passage of lightthrough the chamber H to and fromthe reflectingsurfaces and also because of the unusually large area of the reflectingsurfaces provided on our indicator.

This application is a continuation-in-part of our application Serial No.768,960, filed August 16, 1947, which has been abandoned.

Having described our invention, what we claim as new and desire toprotect by Letters Patent is:

l. A vent plug and liquid level indicator for storage batteriescomprising, a vent chamber having top and bottom walls formed with ventopenings and an outer side wall formed to close anopening in a batterycover, a relatively large, completely closed and sealed central chamberformed from transparent material and having a lower end surface adaptedto be submerged'in the battery electrolyte and shaped to reflectupwardly light passing down through the hollow interior of said chamber,said central chamber extending to thetop of said vent chamber and havingupper end and lower end closures, a legend located within the hollowinterior of said sealed central chamber at an elevation above storagebatteries comprising, an annular vent chamber formed from transparentplastic material and having top and bottom walls formed with ventopenings and an outer side ;wall formed to close an opening in a batterycover, a relatively large, completely closed and sealed central chamberformed from transparent material integrally with the bottom wall of saidannular vent chamber and having a lower end surface adapted to besubmerged in the battery electrolyte and shaped to reflect upwardlylight passing down through the hollow interior of said chamber, saidcentral chamber extending to the top of said vent chamber and havingupper end and lower end closures and a legend adaptedto indicate theneed for adding liquid to the bat tery electrolyte carried by the uppersurface ofsaid lower end closure within said central chamber, saidlegend being illuminated by light reflected from said lower end surfaceand being readable through said upper end closure when the liquid in thebattery is below the said lower end surface and being obscured when saidlower end surface is submerged in the battery liquid.

3. A vent plug and liquid level indicator for storage batteriescomprising, an annular vent chamber having top and bottom Walls formedwith vent openings and an outer side wall formed to close an opening ina battery cover, a relatively large, vertically elongated centralchamber formed from transparent material and having relatively thin sidewalls and a lower end surface adapted to be submerged in the batteryelectrolyte and shaped to reflect upwardly light passing down throughthe hollow interior of said chamber, said central chamber beingcompletely closed and sealed and extending to the top of said ventchamber and having upper end and lower end closures, said upper endclosure being integral with the top Wall of said vent chamber and thevent chamber having an inner circumferential wall portion comprising anannular flange formed integrally with said upper end closure anddepending therefrom in continuation of and in sealed relation to theside walls of said central chamber, whereby the joint between saidannular flange and said walls is substantially concealed at the innercircumference of said annular vent chamber.

FRANK M. BROWN. KENNETH DAWKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

